The present invention relates to a conveying mechanism conveying an object to be conveyed by rotation of a conveying roller, a rotation detecting mechanism mounted on the conveying mechanism and detecting the rotation amount of the conveying roller, and a head suspension assembly used in the rotation detecting mechanism.
Generally, a conveying mechanism for conveying paper or the like is mounted on a printer, a copying machine or the like. In the conveying mechanism, an encoder for controlling rotating operation of a conveying roller for paper feed is provided to control a paper feed position. For example, there is an encoder constructed as follows. A disc in which a plurality of slits are formed is attached to an end of the conveying roller and transmission light leaked from the slits when the disc is irradiated with light is detected by an optical sensor or the like, thereby obtaining the rotation amount of the conveying roller. Further, another encoder is also disclosed in which a magnetic disk having a magnetic pole pattern on its surface and a magnetic drum are rotated synchronously with a conveying roller to generate a magnetic signal corresponding to the magnetic pattern and, by detecting the magnetic signal by a magneto-resistive effect (MR) element, the rotation amount of the conveying roller is obtained (refer to, for example, Japanese Patent Laid-open Nos. 2001-74499 and 2002-206950).
In recent years, the improvement of precision in controlling the paper feed position is being demanded. The improvement of precision in controlling the paper feed position is achieved by, for example, improving detection precision by increasing the size of a medium such as a disc or a magnetic drum and accurately adjusting the rotation center axis of a conveying roller so that stabler rotating operation can be performed.
Recently, as a printer, a copying machine, and the like are being miniaturized, miniaturization of the encoder is in increasing demand. In the encoder as described above, however, the rotation amount is detected without making the sensor come into contact with a medium, so that some intervals of the slits and some dimension of the magnetic pattern are necessary to assure resolution. Therefore, the miniaturization is regulated by the medium. To miniaturize the medium, a method of arranging the medium and the sensor more closely to each other and assuring a stable interval may be employed. For this method, however, the whole conveying mechanism has to be constructed with extremely high precision. Moreover, the mechanism itself is complicated and the number of parts increases. Therefore, it is disadvantage from the cost viewpoint. Further, there is also the possibility that the method is influenced also by the dimension precision of an object to be conveyed such as paper. As a result, it is very difficult to actually realize the method.